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3 T3A: Radio wave characteristics; how a radio signal travels; distinctions of HF, VHF, and UHF; fading, multipath; wavelengths vs. penetration; antenna orientation. T3A1 Should another operator reports that your stations 2 meter signals were strong just a moment ago, but now they are weak or distorted, try moving a few feet, as random reflections may be causing multi-path distortion. T3A2 UHF signals are often more effective from inside buildings than VHF signals as the shorter wavelength allows them to more easily penetrate the structure of buildings. UHF signals are short enough in wavelength to permit bouncing around inside buildings and penetrating of walls.

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4 T3A: Radio wave characteristics; how a radio signal travels; distinctions of HF, VHF, and UHF; fading, multipath; wavelengths vs. penetration; antenna orientation. T3A3 Horizontal antenna polarization is normally used for long- distance weak-signal CW and SSB contacts using the VHF and UHF bands. T3A4 Signals could be significantly weaker if the antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization. Transmitter to Receiver – Radio waves from transmitting antennas induce signals in receiving antennas as they pass by

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5 T3A: Radio wave characteristics; how a radio signal travels; distinctions of HF, VHF, and UHF; fading, multipath; wavelengths vs. penetration; antenna orientation. T3A5 When using a directional antenna, your station might be able to access a distant repeater if buildings or obstructions are blocking the direct line of sight path by finding a path that reflects signals to the repeater. Directional Antenna can be used to bounce signal to reach repeater blocked by building

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6 T3A: Radio wave characteristics; how a radio signal travels; distinctions of HF, VHF, and UHF; fading, multipath; wavelengths vs. penetration; antenna orientation. T3A6 Picket fencing is the term commonly used to describe the rapid fluttering sound sometimes heard from mobile stations that are moving while transmitting. T3A7 Electromagnetic waves carry radio signals between transmitting and receiving stations. T3A8 The cause of irregular fading of signals from distant stations during times of generally good reception is due to random combining of signals arriving via different path lengths.

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7 7 T3A: Radio wave characteristics; how a radio signal travels; distinctions of HF, VHF, and UHF; fading, multipath; wavelengths vs. penetration; antenna orientation. T3A9 A common effect of "skip" reflections between the Earth and the ionosphere is the polarization of the original signal becomes randomized. Skip happens when signals refract and reflect off the ionosphere. DX stations 1000 miles away come booming in. Every 30 seconds signal goes from strong to weak and back. Caused by random, ever changing polarization of the original signal. Critical Frequency

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8 T3A: Radio wave characteristics; how a radio signal travels; distinctions of HF, VHF, and UHF; fading, multipath; wavelengths vs. penetration; antenna orientation. T3A10 Error rates are likely to increase on VHF or UHF data signals propagated over multiple paths. T3A11 The ionosphere is the part of the atmosphere that enables the propagation of radio signals around the world. Ionosphere and its layers

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9 9 T3B: Radio and electromagnetic wave properties; the electromagnetic spectrum, wavelength vs. frequency, velocity of electromagnetic waves. T3B1 The name for the distance a radio wave travels during one complete cycle is wavelength. Keywords: distance and wavelength T3B2 The term that describes the number of times per second that an alternating current reverses direction is frequency. 0V V+V+ V- One Cycle time One Wavelength

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10 T3B: Radio and electromagnetic wave properties; the electromagnetic spectrum, wavelength vs. frequency, velocity of electromagnetic waves. T3B3 Electric and magnetic fields are the two components of a radio wave.  T3B4 Radio waves travel through free space at the speed of light.  T3B11 The approximate velocity of a radio wave as it travels through free space is 300,000,000 meters per second.

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11 T3B: Radio and electromagnetic wave properties; the electromagnetic spectrum, wavelength vs. frequency, velocity of electromagnetic waves. T3B6 The formula for converting frequency to wavelength in meters is the wavelength in meters equals 300 divided by frequency in megahertz. (One answer ends with word Megahertz) T3B5 The wavelength of a radio wave relates to its frequency inversely, as the wavelength gets shorter the frequency increases. Higher in frequency the shorter the distance between each wave. T3B7 The property of radio waves often used to identify the different frequency bands is the approximate wavelength. Wavelength of the band: 2 meters; 20 meters; 40 meters, etc

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12 T3B: Radio and electromagnetic wave properties; the electromagnetic spectrum, vs. frequency, velocity of electromagnetic waves. T3B10 The frequency range referred to as HF is 3 MHz to 30 MHz. T3B8 The frequency limits of the VHF spectrum are 30 MHz to 300 MHz. T3B9 The frequency limits of the UHF spectrum are 300 MHz to 3000 MHz.

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14 T3C: Propagation modes; line of sight, sporadic E, meteor, aurora scatter, tropospheric ducting, F layer skip, radio horizons T3C2 When VHF signals are being received from long distances these signals are being refracted from a sporadic E layer. T3C3 A characteristic of VHF signals received via auroral reflection is that the signals exhibit rapid fluctuations of strength and often sound distorted. Incoming signals from a distant station heard hundreds of miles away will sound fluttery and distorted by auroral bounce

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18 T3C: Propagation modes; line of sight, sporadic E, meteor, aurora scatter, tropospheric ducting, F layer skip, radio horizons T3C9 During daylight hours is generally the best time for long-distance 10 meter band propagation. T3C10 The distance at which radio signals between two points are effectively blocked by the curvature of the Earth is the radio horizon. VHF & UHF radio signals will generally travel “line of sight.” VHF & UHF radio signals are blocked by the curvature of the Earth. T3C11 VHF and UHF radio signals usually travel somewhat farther than the visual line of sight distance between two stations because the Earth seems less curved to radio waves than to light. the Earth seems less curved to VHF and UHF radio signals.

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20 T3A01 What should you do if another operator reports that your station’s 2 meter signals were strong just a moment ago, but now they are weak or distorted? A.Change the batteries in your radio to a different type B.Turn on the CTCSS tone C.Ask the other operator to adjust his squelch control D.Try moving a few feet, as random reflections may be causing multi-path distortion

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21 T3A02 Why are UHF signals often more effective from inside buildings than VHF signals? A.Change the batteries in your radio to a different type B.The shorter wavelength allows them to more easily penetrate the structure of buildings C.This is incorrect; VHF works better than UHF inside buildings D.UHF antennas are more efficient than VHF antennas

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23 T3A04 What can happen if the antennas at opposite ends of a VHF or UHF line of sight radio link are not using the same polarization? A.The modulation sidebands might become inverted B.Signals could be significantly weaker C.Signals have an echo effect on voices D.Nothing significant will happen

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24 T3A05 When using a directional antenna, how might your station be able to access a distant repeater if buildings or obstructions are blocking the direct line of sight path? A.Change from vertical to horizontal polarization B.Try to find a path that reflects signals to the repeater C.Try the long path D.Increase the antenna SWR

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25 T3A06 What term is commonly used to describe the rapid fluttering sound sometimes heard from mobile stations that are moving while transmitting? A.Flip-flopping B.Picket fencing C.Frequency shifting D.Pulsing

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27 T3A08 What is the cause of irregular fading of signals from distant stations during times of generally good reception. A.Absorption of signals by the "D" layer of the ionosphere B.Absorption of signals by the "E" layer of the ionosphere C.Random combining of signals arriving via different path lengths D.Intermodulation distortion in the local receiver

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28 T3A09 Which of the following is a common effect of "skip" reflections between the Earth and the ionosphere? A.The sidebands become reversed at each reflection B.The polarization of the original signal is randomized C.The apparent frequency of the received signal is shifted by a random amount D.Signals at frequencies above 30 MHz become stronger with each reflection

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29 T3A10 What may occur if VHF or UHF data signals propagate over multiple paths? A.Transmission rates can be increased by a factor equal to the number of separate paths observed B.Transmission rates must be decreased by a factor equal to the number of separate paths observed C.No significant changes will occur if the signals are transmitting using FM D.Error rates are likely to increase

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30 T3A11 Which part of the atmosphere enables the propagation of radio signals around the world? A.The stratosphere B.The troposphere C.The ionosphere D.The magnetosphere

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31 T3B01 What is the name for the distance a radio wave travels during one complete cycle? A.Wave speed B.Waveform C.Wavelength D.Wave spread

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32 T3B02 What term describes the number of times per second that an alternating current reverses direction? A.Pulse rate B.Speed C.Wavelength D.Frequency

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33 T3B03 What are the two components of a radio wave? A.AC and DC B.Voltage and current C.Electric and magnetic fields D.Ionizing and non-ionizing radiation

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34 T3B04 How fast does a radio wave travel through free space? A.At the speed of light B.At the speed of sound C.Its speed is inversely proportional to its wavelength D.Its speed increases as the frequency increases

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35 T3B05 How does the wavelength of a radio wave relate to its frequency? A.The wavelength gets longer as the frequency increases B.The wavelength gets shorter as the frequency increases C.There is no relationship between wavelength and frequency D.The wavelength depends on the bandwidth of the signal

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36 T3B06 What is the formula for converting frequency to wavelength in meters? A.Wavelength in meters equals frequency in hertz multiplied by 300 B.Wavelength in meters equals frequency in hertz divided by 300 C.Wavelength in meters equals frequency in megahertz divided by 300 D.Wavelength in meters equals 300 divided by frequency in megahertz

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37 T3B07 What property of radio waves is often used to identify the different frequency bands? A.The approximate wavelength B.The magnetic intensity of waves C.The time it takes for waves to travel one mile D.The voltage standing wave ratio of waves

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38 T3B08 What are the frequency limits of the VHF spectrum? A.30 to 300 kHz B.30 to 300 MHz C.300 to 3000 kHz D.300 to 3000 MHz

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39 T3B09 What are the frequency limits of the UHF spectrum? A.30 to 300 kHz B.30 to 300 MHz C.300 to 3000 kHz D.300 to 3000 MHz

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41 T3B11 What is the approximate velocity of a radio wave as it travels through free space? A.3000 kilometers per second B.300,000,000 meters per second C.300,000 miles per hour D.186,000 miles per hour

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42 T3C01 Why are "direct" (not via a repeater) UHF signals rarely heard from stations outside your local coverage area? A.They are too weak to go very far B.FCC regulations prohibit them from going more than 50 miles C.UHF signals are usually not reflected by the ionosphere D.They collide with trees and shrubbery and fade out

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43 T3C02 Which of the following might be happening when VHF signals are being received from long distances? A.Signals are being reflected from outer space B.Signals are arriving by sub-surface ducting C.Signals are being reflected by lightning storms in your area D.Signals are being refracted from a sporadic E layer

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44 T3C03 What is a characteristic of VHF signals received via auroral reflection? A.Signals from distances of 10,000 or more miles are common B.The signals exhibit rapid fluctuations of strength and often sound distorted C.These types of signals occur only during winter nighttime hours D.These types of signals are generally strongest when your antenna is aimed to the south (for stations in the Northern Hemisphere)

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46 T3C05 What is meant by the term "knife-edge" propagation? A.Signals are reflected back toward the originating station at acute angles B.Signals are sliced into several discrete beams and arrive via different paths C.Signals are partially refracted around solid objects exhibiting sharp edges D.Signals propagated close to the band edge exhibiting a sharp cutoff

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50 T3C09 What is generally the best time for long- distance 10 meter band propagation? A.During daylight hours B.During nighttime hours C.When there are coronal mass ejections D.Whenever the solar flux is low

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51 T3C10 What is the radio horizon? A.The distance at which radio signals between two points are effectively blocked by the curvature of the Earth B.The distance from the ground to a horizontally mounted antenna C.The farthest point you can see when standing at the base of your antenna tower D.The shortest distance between two points on the Earth's surface

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52 T3C11 Why do VHF and UHF radio signals usually travel somewhat farther than the visual line of sight distance between two stations? A.Radio signals move somewhat faster than the speed of light B.Radio waves are not blocked by dust particles C.The Earth seems less curved to radio waves than to light D.Radio waves are blocked by dust particles